1. Field of the Invention
The present invention relates to a Ziegler-Natta catalyst, and particularly to a method for making the catalyst and a method for using the catalyst in a polymerization reaction.
2. Background of the Art
Ziegler-Natta catalysts are advantageously used in olefin polymerization reactions to produce stereoregulated linear polymers. Typically, such catalysts include a trialkyl aluminum (e.g., triethyl aluminum) in combination with a transition metal compound such as titanium chloride as co-catalyst. Generally, the Ziegler-Natta catalysts are small, solid particles, but soluble forms and supported catalysts have also been used.
Ziegler-Natta catalysts are especially useful for the homopolymerization and copolymerization ethylene, proplylene, and other alk-1-enes to produce films, fibers and moldings.
U.S. Pat. Nos. 5,162,465 and 5,006,620 disclose the preparation of polymers of propene using a Ziegler-Natta catalyst system consisting of a titanium component which is based on a finely divided, shape-imparting silica gel and contains, in addition to titanium, magnesium, chlorine and a benzenecarboxylic acid derivative, an aluminum component and a silane component. Both patents have in common that the impregnation of the supporting particle is performed using magnesium organic precursor compounds. These compounds are, in general, air and moisture sensitive and require additional solvent addition to the catalyst preparation process. Secondly, the conversion of the magnesium organic precursor compound to the magnesium halide is conducted using halogenating agents like chlorine or hydrogen chloride, which are in general considered as hazardous and environmentally unfriendly compounds.
It would be advantageous to simplify the catalyst preparation and minimize costs and environmental contamination due to waste streams and starting materials.
A method is provided herein for making a solid catalyst component for use in a Ziegler-Natta catalyst. The method comprising the steps of: (a) combining a porous particulate support with a magnesium source in a hydrocarbon solvent to form a slurry mixture, the magnesium source including a hydrocarbon soluble organomagnesium compound and an inorganic magnesium-halogen compound; (b) halogenating the organomagnesium compound; (c) reacting the slurry mixture with a titanium compound or vanadium compound to form the solid catalyst component; and (d) recovering the solid catalyst component.
The solid catalyst component can be combined with an organoaluminum cocatalyst to provide a Ziegler-Natta catalyst useful for the polymerization of olefins.
The method described herein overcomes the above described disadvantages and provides improved catalytic systems of the Ziegler-Natta type. The resulting catalyst has a high activity and allows the production of polymers of xcex1-alk-1-enes having a good morphology and bulk density.